The present invention relates generally to the field of liquid chromatography, and relates particularly to a self-diagnostic gel permeation/size-exclusion chromatograph and method for determining the molecular weights and molecular weight distribution of polymers.
Polymers such as polystyrene and saran resins comprise a wide distribution of molecular size/molecular weights. The weight/size distribution for a particular polymer typically has a characteristic shape. Accordingly, one important way of controlling the properties of a polymer is to control the shape of its molecular weight/size distribution.
In view of the above, there is a present and growing need to generate routine molecular weight/size information in polymer production plants and laboratories. However, in order for this information to be meaningful, it must be sufficiently accurate to permit comparison with similar information generated by other polymer production plants.
The type of chromatograph which is capable of generating molecular weight/size distributions for polymers is generally referred to as a size-exclusion chromatograph (SEC) or a gel permeation chromatograph (GPC). While these terms are not precisely synonymous, they are both commonly used to describe the same chromatographic technique. To simplify the language below, these chromatographs will generally be referred to as SEC/GPC chromatographs. While there are several commercially available SEC/GPC chromatographs, these instruments have generally been designed with the assumption that the principal users will be chromatographers who possess the needed skills and experience to generate accurate results. As well known in the art, special skills and experience are needed to both correctly perform SEC/GPC measurements, and to correctly interpret the data generated. These commercial instruments also lack the diagnostics generally necessary for reliable, full-time operation outside of a research laboratory.
Accordingly, it is a principal object of the present invention to provide an SEC/GPC chromatograph which does not require any particular chromatographic expertise to successfully and reliably produce precise and molecular weight/size information in the field.
It is another object of the present invention to provide an SEC/GPC chromatograph which assures compatibility with the data generated by similar chromatographs located in other polymer production plants.
It is an additional object of the present invention to provide an SEC/GPC chromatograph which incorporates several self-diagnostic features that eliminate the need for an experienced chromatographic practitioner to operate the instrument and permit semi-automated operation.
It is yet another object of the present invention to provide an SEC/GPC chromatograph which is capable of substantially decreasing the test time required to analyze a series of polymer samples.
It is yet another object of the present invention to provide an SEC/GPC chromatograph which has the capability of refilling the eluant or solvent reservoir within the chromatograph by remote control. A convenient way of measuring the eluant liquid level within the chromatograph reservoir is also provided.
It is yet a further object of the present invention to provide an improved oven construction for a SEC/GPC chromatograph which permits convenient adjustment of the detector optical zero response.
It is still another object of the present invention to provide a SEC/GPC chromatograph which will automatically revert to a controlled shut down mode or a recycle mode when predetermined malfunctions have been detected.
It is a still further object of the present invention to provide a rugged SEC/GPC chromatograph which is capable of producing long term reproducible results.